Is it Possible to have Two Alternating Pistons in Blender Physics?
Robin Betts comment was probably the closest I was looking for.
However, in the meantime I have switched to  a more simple mechanism proposed by the students of Delf TU in Holland.
Here is how I rendered it.


They key in making this happen is by setting the piston to Animated and building keyframes on it. The rest moves by itself through Physics.
Thanks to all!